MARKETABLE SECURITIES - Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Marketable securities	$ 250,408	$ 191,799
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Marketable securities	37,251	31,864
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities	173,669	125,547
Securities of government sponsored entities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities	$ 39,488	$ 34,388